There's so much equipment to loot or buy in in the form of armor, weapons, and accessories with special, unlockable abilities that can be accessed as Rook trades the Caretaker for upgrades.Equipment in can be found or purchased, but not crafted.
However, once Rook recruits Bellara, and she repairs the Eluvian on the lower level of the Lighthouse, granting access to The Crossroads, Rook can meet the Caretaker, who can help outfit them for battle with both faction enemies and blighted gods.
Gear upgrades in increase an item's stats and unlock special additional abilities. This is true not only for Rook's gear, but for their companions' items as well.
Gear can also be enchanted to apply additional, custom effects to equipment that should fit any playstyle. To make these upgrades, Rook will need to visit — and upgrade — the Caretaker's Workshop. At the Lighthouse, outside the library, Rook can find the Workshop below the giant wolf statue.
The Caretaker will appear here when called upon and can help Rook upgrade their team's gear. In general, Rook can upgrade every item in their inventory one time per Workshop level, provided they have enough materials to do so.